Prevention is recognized as the most important ingredient of good dental care. Cavities are now recognized to be of bacterial origin; bacteria in the mouth combine with sugars, remaining on or between the teeth to produce acid that destroys tooth enamel and eats into the heart of the tooth. Limiting the amount of ingested sugar can reduce the incidence of cavities. Unfortunately, such self limitation in most population groups usually remains modest and is easily reversible. For this reason automatic caries-preventive measures such as fluoridated water, fluoride toothpastes and rinses and fluoride-supplemented vitamins and foodstuffs have been developed.
Studies have shown that marked caries reduction can be obtained by bicarbonate-phosphate or bicarbonate-phosphate-fluoride combinations mixed into the dietary sugar of rats. (Luoma, et. al., Caries Res., 4, pp. 332-346 (1970)). Other studies in a controlled population of institutionalized mentally handicapped children have shown that the inclusion of fluoride and a bicarbonate-phosphate mixture in sweet sugar products of the children's diet produces caries arrestment after the first year. (Luoma, et. al., Scand. J. Dent. Res., 87, pp. 197-207 (1979). In these studies, Luoma added the bicarbonate fraction mainly to serve as the buffering agent while the phosphate component (a divalent anion) was added to satisfy the phosphate need of cariogenic bacteria in order to prevent the enamel phosphate from being utilized for the bacteria's metabolic need.
Both thiocyanate and chloride anions have recognized roles in lactoperoxidase and myeloperoxidase antibacterial systems (Jago and Morrison, Proc. Soc. Exp. Biol. Med., 111, pp 585-588 (1962); Zeldow, J. Immunol., 90, pp. 12-16 (1963); and Klebanoff, J. Bacteriol., 95, pp 2131-2138 (1968)).
The antibacterial effects of fluoride have been known for many years (Bibby and VanKesteren, J. Dent. Res., 19, pp. 391-402 (1940)) and bicarbonate has been proposed to stabalize the iron binding properties of human milk lacteroferrin (Masson and Hermens, Eur. J. Biochem., 6, pp. 579-584 (1968)).
The concentrations of each of these anions have been observed to vary with salivary flow rate and with duration of collection at fixed flow rates. (Dawes, Archs. Oral. Biol. 14, 277 (1969); Jenkins, "The Physiology and Biochemistry of the Mouth", 4th ed, pp. 284-359 (1978); Kreusser, et. al., Eur. J. Clin. Invest., 2, pp 398-406, (1972). Natural, normal physiological concentrations in submandibular parotid and mixed human salivas range for bicarbonate from about 1-60 mM, for chloride from 10 to 50 mM and thiocyanate from 0.5 to 4.5 mM (Jenkins, supra). After a mouth rinse for two minutes with 0.2% sodium fluoride, salivary fluoride concentrations were found to average 36 millimolar (Bruun, et. al., Communits. Dent. Oral. Epidemiol., 10, pp. 174-129 (1982)). These concentrations, naturally occurring or otherwise, are ineffective individually to lyse and therefore kill caries bacteria. It has now been found that compositions containing bicarbonate anion and a monovalent anion act synergistically so that compositions together containing a subeffective amount of both the bicarbonate anion and the monovalent anion are effective agents for anti-caries therapy.